The CAS Registry Mumber 82176-64-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,1,7 and 6 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 82176-64: (7*8)+(6*2)+(5*1)+(4*7)+(3*6)+(2*6)+(1*4)=135 135 % 10 = 5 So 82176-64-5 is a valid CAS Registry Number.